A puzzle is a toy that tries the ingenuity and taxes the patience of a player. A puzzle game usually involves the selection and sequential assembly of a plurality of polygonal sheet pieces of varying contour, to recreate an original image about a flat sheet board. More complex puzzle games include assembling a three-dimensional self-standing structure with a variety of puzzle pieces, along edgewisely interlocked horizontal and vertical walls.
An example of the latter type of three dimensional puzzle can be found in the recent U.S. Pat. No. 4,824,112 issued in April 1989 to Roy. An inconvenience with such a puzzle is that non-planar puzzle pieces have to be used, more particularly at the corners of two transverse walls of the self-standing assembled structure--see FIG. 7a of the Roy reference. This means that two different dies are required for the manufacture of the puzzle pieces: one for the flat, planar pieces, and another for the bent corner pieces. This is inefficient.
Other three-dimensional puzzles rely for their self-standing capability onto locking pins or the like, for anchoring the corner edge portions of pairs of transverse walls forming part of the puzzle. This can be found in U.S. Pat. No. 2,569,107 to Johnson. Again, this requires additional particular means distinct from the puzzle pieces as such, a manufacturing inefficiency.
A three-dimensional, self-standing puzzle structure made exclusively of planar puzzle pieces, is disclosed in U.S. Pat. No. 3,701,214 issued in 1972 to the Kyoikushuppan Co of Japan (kyoi'). In this patent, each puzzle piece is a flat polygonal block having dovetail joints at its edgewise sections for interlocking engagement with complementary, edgewise, dovetail joints of adjacent puzzle pieces. Adjacent blocks are interlocked by engagement of mating, male and female, complementary dovetail joint elements.
The Kyoi' patent is interesting, however, it must be quite difficult to assemble the corner parts of the self-standing structure, if each wall is made from a number of puzzle pieces, since the dovetail male element of a first block cannot by definition engage the dovetail female element of a second block within the plane of any of these two blocks. More particularly, as is well known in the art, to interlock male and female dovetail joint elements, they must first be brought in transverse register with one another, and then inserted sidewisely through their planes. The male dovetail element certainly cannot be inserted head on through the mouth of the female dovetail element.
Hence, it is not seen how a complete, enclosed, self standing, continuous, three dimensional structure could be made with the Kyoi' puzzle pieces, where each wall is constituted by more than one puzzle piece. Indeed, the Kyoi' patent would probably enable erection of a building structure having two or three, multiple puzzle piece walls, but a fourth and last wall of the building structure enclosing same could not in fact be installed to the two opposite side walls, because the dovetail joints interlocking axis would prevent positioning of the fourth wall edgewisely against the two side walls.
FIG. 8 of the Kyoi' patent suggests that an enclosed, albeit discontinuous structure could be constructed with the dovetail joint puzzle pieces thereof. However, for this to occur, each wall of the structure must consist of a single puzzle piece, as illustrated in the figure. Having a self-standing structure with a single modular unit for each wall is not considered by applicant to constitute a true puzzle. In any event, the image from FIG. 8 of the Kyoi' patent is discontinuous at the corner edges thereof.